The invention relates to an antitumor agent containing a novel compound discovered by a new screening method that the inventors of the invention have developed, as an active ingredient. The compound, which has a pentitol and a hexitol chain as an aglycone, and in which all hydroxyl groups of a mannose ring which is a mother nucleus are esterified with medium chain fatty acids, is particularly an excellent novel glycolipid glycoside which inhibits a proliferation of tumor cells and are useful as an antitumor agent.
The glycolipid glycoside of the invention has been unknown to have an antitumor action.
As a sugar fatty acid ester compound is known a compound in which all hydroxyl groups of a mannose ring became a fatty acid ester is known (Patent Literature 1).